“The Man Who Evolved,” Edmond Hamilton, 1931 – A man uses cosmic rays to evolve into a giant brain.
Comments: Read in Before the Golden Age, Book One, ed. Isaac Asimov. Asimov’s afterward critiques the science, i.e., populations evolve, not individuals.
Author: Wikipedia: “Edmond Moore Hamilton (October 21, 1904 – February 1, 1977) was an American author of science fiction stories and novels during the mid-twentieth.” “World-wrecker” Hamilton was an extremely prolific writer, particularly of space opera, and appeared frequently in Weird Tales. He was close friends with many prominent genre writers, including Jack Williamson, and was married to Leigh Brackett, a science fiction writer and a screen writer of several notable screenplays.